The present invention is directed toward mechanical disc brakes, and more particularly toward a cable feed apparatus and method for connecting a cable to a mechanical disc brake.
Disc brakes are being included on more and more bicycles as consumers are ever increasingly demonstrating a preference for disc brakes over conventional rim brakes such as caliper brakes, cantilever brakes and side pull cantilever brakes. While both mechanical and hydraulic disc brakes have been available for bicycles for many years, only recently have there been advances in mechanical disc brake caliper design that have made mechanical disc brakes sufficiently lightweight, powerful, reliable and inexpensive to satisfy consumer preferences. While more efficient and powerful cable actuated mechanical disc brakes are evolving, to date manufacturers of mechanical disc brakes have not adequately addressed providing an efficient cable feed that minimizes friction on the cable as well as cable fatigue.
One known cable feed structure for a cable actuated mechanical disc brake caliper provides a cable guide on the housing which functions at a cable housing stop and guide to direct cable to an actuating lever of the cable actuated mechanical disc brake caliper. The cable guide of this cable actuated mechanical disc brake is pivotably attached to the caliper housing. While this pivotal attachment is intended to direct the cable on a straight line between the guide and the pivoting actuating arm of the caliper brake, it presents a serious problem because of the possibility of grit or debris causing the pivotal attachment to seize in a pivoted position that introduces a bend to the cable. With time, such a bend can introduce fatigue and possible failure to the cable, with disastrous results to the rider.
There remains a need to provide a cable feed for a cable actuated mechanical disc brake caliper which minimizes or eliminates bends in the cable as it is fed and attached to an actuating arm of the caliper to minimize fatigue as well as friction on the cable which can degrade the performance of the brake.
The present invention is directed toward overcoming one or more of the problems discussed above.
A cable actuated bicycle mechanical disc brake caliper includes caliper housing and a cable guide rigidly fixed to the housing with the cable guide having a cable receiving bore extending along a guide axis for axially receiving a cable. A lever arm is pivotably attached to the caliper housing for pivoting about a pivot axis. The lever arm is operatively associated with a brake pad to move the brake pad between a retracted and an extended position as the lever arm is pivoted in a first direction from a non-actuated position to a fully actuated position. The lever arm includes a cable clamp spaced from the pivotal attachment for fixedly attaching a cable to the lever arm in a select orientation relative to the lever arm at an attachment point. The attachment point is essentially coincident with the guide axis with the cable arm in the fully actuated position.
A second aspect of the present invention is a cable actuated mechanical disc brake caliper including a caliper housing having a cable guide rigidly fixed to the housing with the cable guide having a cable receiving bore extending along a guide axis for axially receiving a cable. A lever arm is pivotably attached to the caliper housing for pivoting about a pivot axis with the lever arm being operatively associated with a brake pad to move the brake pad between a retracted and an extended position as the lever arm is pivoted in a first direction from a non-actuated position to a fully actuated position. The lever arm includes a cable clamp circumferentially spaced from the pivotal attachment for fixedly attaching a cable to the lever arm in a select orientation relative to the lever arm at an attachment point. A guide surface which is curved about the pivot axis has a first portion attached to the lever arm with the attachment point essentially coincident therewith. A second portion is circumferentially spaced from the first portion and the second portion is essentially tangent to the guide axis with the lever arm in the non-actuated position. The curved surface may be concentric about the pivot axis. Alternatively, the curved surface is eccentric about the pivot axis and the radius of the curved surface may either increase or decrease between the first and second portions. The cable clamp preferably clamps along an axis normal to the pivot axis. The curved surface is preferably formed by a horn attached to the lever arm at the first portion with the second portion being a free end of the horn.
Yet another aspect of the present invention is a method of directing a cable to a lever arm of a cable actuated mechanical disc brake caliper wherein the lever arm is pivotably attached to a housing of the brake caliper for pivoting about a pivot axis. The lever arm is operatively associated with a brake pad to move the brake pad between a retracted and an extended position as the lever arm is pivoted in a first direction from a non-actuated position to a fully actuated position. The method includes providing a cable guide rigidly attached to the caliper defining a cable guide axis a select radial distance from the pivot axis. A cable is fed through the cable guide and attached to the lever arm at an attachment point about the select radial distance from the pivot axis. The cable is maintained essentially tangent to the guide axis as the lever is pivoted between the non-actuated and the actuated positions.
The cable guide structure and method of attaching a cable to a lever arm of a cable actuated mechanical disc brake in accordance with the present invention provides for efficient attachment of the cable to the lever arm which minimizes friction on the cable to improve brake performance. The method and cable feed structure further eliminate the possibility of any bends or kinks in the cable which could fatigue and possibly lead to failure of the cable. The structure and method are accomplished without moving parts, which both simplifies assembly and reduces the cost of the mechanically actuated disc brake caliper. Furthermore, elimination of moving parts provides for a highly reliable cable actuated mechanical disc brake caliper.